My 97 540I automatic has a loud roaring noise at slight pulling. When given more gas, or let off gas, it stops. Does it at 30 or 70.
It's loud. I've had BMW locally check it and they like the other mechanics that have looked at it say keep on driving, turn up the radio until it breaks then we can fix it.
Everything works just great.
Any of you BMW experts have any ideas?

its from the middle to back underneath. They checked out wheel bearings, differential and tranny oil and just don't know. Can't get it to do it on rack.
Very loud, can't miss it. Rubbing roar. Checked out tires and no rub spots.

Funny how it won't do it coasting or when giving more gas, only at cruising gas amount. Stops immediately when let off gas or put in neutral no matter what speed.

I'd be looking at the center support bearing going bad on the driveshaft (it's under a heat shield above the exhaust and not the easiest to check). The u joints get old and aren't serviceable so it's a driveshaft replacement if that's what's happening. Rule of thumb if the center support goes out, don't waste your time replacing it. You'll be doing the whole shaft in a couple more weeks/months when that one fails too (and it will).

That's really about the only other spinning thing down there that can be doing it, so it's worth the effort to check.

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Big Evil, The BMW driving monster of the American Southwest (Currently on BMW #5)

Check exhaust hangers and motor mounts. I don't remember if your year had an inertial isolator on the exhaust (basically a big weight bolted it on to eliminate resonance frequencies at cruising speeds)

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Big Evil, The BMW driving monster of the American Southwest (Currently on BMW #5)

I get the same thing after the engine gets up to temp. A '95 525i and it has always made that noise. The mechanic tells me it's the radiator fan clutch. It has always made that noise, even new ones sound loud. Have to live with it, roll the windows up, turn up the radio.